Thin-layer chromatographic and high-performance thin-layer chromatographic ready-for-use layers with lipophilic modifications

Stable silica gel sorbents with aliphatic or aromatic groups are formed by chemical modifications of the silanol groups with special reactive silanes. Various lipophilic surface modifications on silica gels with varying pore structures are tested with regard to their chemical and physico-chemical characteristics, their wettability and their chromatographic retention data. The main problem in TLC is the preparation of abrasion-resistant layers on glass or on foils which meet the usual high standard of quality and are also suited for quantitative determinations. Thin-layer chromatography on reversed-phase layers can only be performed if the complete wettability of the lipophilic stationary phase in dry form is guaranteed by the mobile phase. Adsorption-chromatographic separations with lipophilic eluents and reversed-phase partition-chromatographic separations with hydrophilic eluents are performed, for example, with dyes, with polycyclic aromatic hydrocarbons and with lipids. The great differences in selectivity caused by the various modifications of the sorbent and the varying eluent composition are remarkable. Ready-for-use layers with lipophilic surface modifications complement the existing range of pre-coated layers and thus widen the application of TLC and HPTLC considerably.     

Lipophilic constituents from two processed products and three different parts of Changium smyrnioides Wolff.

This article reports the lipophilic chemical composition of different processed products (Changii Radix, Changii Radix Alba) and parts (root bark, leaf and fruit) of Changium smyrnioides Wolff.. The lipophilic constituents were extracted with petroleum ether in Soxhlet apparatus, subsequently identified and determined by gas chromatography–mass spectroscopy (GC–MS). Yield of lipophilic constituents from Changii Radix (3.65%) was about three times more than Changii Radix Alba's (1.07%), which indicated processing by boiling in water had an impact on the content of lipophilic constituents. Moreover, the major compounds in different processed products and parts were found to be fatty acids and sesquiterpenes. The results are a contribution for the lipophilic chemical composition and can serve as a reference for product development of Changium smyrnioides Wolff..     

Lipophilic Tartaric Acid Esters as Enantioselective Ionophores

Tartaric acid esters with lipophilic alcohol moieties can discriminate between enantiomeric ammonium ions such as norephedrinium ions. Quantitative results were obtained by partitioning the components between water and 1, 2-dichloroethane. The stereoselectivity was characterized by the free energy difference of the partition process (ΔΔG). Diamond-lattice sectors were used to construct models of the (unstable) lipophilic ester/ammonium salt complexes from X-ray structures of the individual components (esters and ammonium salts). These models can be used to interpret the effect of structure and configuration of the alcohol moiety on the stereoselectivity and enantioselectivity towards 1-phenyl-2-amino-1-propanol (norephedrine) salts.     

Thermodynamics of the surfaces of nonionic spherical micelles with relatively large extensions of the interfacial layer

The structural properties of nonionic spherical micelles with relatively large extensions of the interfacial layer are investigated, and the size dependences of their adsorption, interfacial tension, and chemical potential are obtained. Such familiar thermodynamic relationships as the Gibbs and Laplace equations, the differential equation for the chemical potential, and the concept of hydrophilic–lipophilic balance are used. The method is applied to micelles formed in surfactant solutions of a homologous series of tetraethylene glycol alkyl ethers. The region of the existence of micellar solutions and the structural characteristics of the interfacial layer of micelles are determined. The interfacial tension minimum corresponding to ideal hydrophilic–lipophilic balance in the micelle interfacial layer is detected. The chemical potential is negative over the range of the homologous series, and its derivative with respect to the tension radius is also negative.

     

Cyclodextrins in Eye Drop Formulations

Ideally, eye drop formulations are aqueous solutions. Many drugs that are useful in topical application to the eye are not sufficiently water soluble to be dissolved in simple aqueous solutions. This problem is approached through hydrophilic prodrugs, suspensions, lipid based solutions and excipients such as cyclodextrins. Cyclodextrins can be used to form aqueous eye drop solutions with lipophilic drugs, such as steroids. The cyclodextrins increase the water solubility of the drug, enhance drug absorption into the eye, improve aqueous stability and reduce local irritation. Cyclodextrins are useful excipients in eye drop formulations of various ophthalmic drugs, including steroids of any kind, carbonic anhydrase inhibitors, pilocarpine and cyclosporins. Their use in ophthalmology has already begun and it is likely to expand the selection of drugs available as eye drops. In this paper we review the use of cyclodextrins in eye drop formulations. The use of cyclodextrins to formulate dexamethasone eye drops is an example of their usefulness. Cyclodextrins have been used to formulate eye drops containing corticosteroids, such as dexamethasone, with concentration and ocular absorption, which in human and animal studies is many fold that seen with presently available formulations. Such formulations offer the possibility of once a day application of corticosteroid eye drops after eye surgery, and more intensive topical steroid treatment in severe inflammation.     

Number of solution states of bradykinin from ion mobility and mass spectrometry measurements

Ion mobility and mass spectrometry measurements have been used to examine the populations of different solution structures of the nonapeptide bradykinin. Over the range of solution compositions studied, from 0:100 to 100:0 methanol:water and 0:100 to 90:10 dioxane:water, evidence for 10 independent populations of bradykinin structures in solution is found. In some solutions as many as eight structures may coexist. The solution populations are substantially different than the gas-phase equilibrium distribution of ions, which exhibits only three distinct states. Such a large number of coexisting structures explains the inability of traditional methods of characterization such as nuclear magnetic resonance spectroscopy and crystallography to determine detailed structural features for some regions of this peptide.     

Reaction of vitamin E compounds with N-nitrosated tryptophan derivatives and its analytical use

We recently showed that nitrosated tryptophan residues may act as endogenous nitric oxide storage compounds. Here, a novel reaction of nitrosotryptophan derivatives is described, in the form of the release of nitric oxide from N-nitrosotryptophan derivatives initiated either by alpha-tocopherol or by its water-soluble form trolox. Alpha-tocopherol and trolox were found to release stoichiometric amounts of nitric oxide from N-acetyl-N-nitrosotryptophan as well as from the nitrosotryptophan residue in albumin. The reaction proceeds both in water and in lipophilic solution and reconstitutes the indole moiety of the tryptophan molecule quantitatively. During this reaction, alpha-tocopherol- and trolox-derived phenoxyl-type radicals were identified as intermediates by ESR spectrometry. The chemical mechanism of the NO-releasing process was established. Since S-nitrosothiols do not react under the applied conditions, it is suggested that the trolox-dependent release of nitric oxide may be utilizable for the detection of N-nitrosotryptophan residues in biological samples. Furthermore, as N-nitrosotryptophan derivatives do not undergo spontaneous decay in lipophilic environments, vitamin E may have the so far unrecognized function of preventing the accumulation of N-nitrosotryptophan residues to toxic concentrations in biological systems.     

Highly oxygenated guaianolides and eudesman-12-oic acids from Balsamorhiza sagittata and Balsamorhiza macrophylla

Investigation of lipophilic exudates from the aerial parts of Balsamorhiza sagittata and B. macrophylla afforded three new highly oxygenated guaianolides (1-3), in addition to known guaianolides, germacranolide and eudesmane acids. Their chemical structures were elucidated by spectroscopic methods and the data for the compounds are reported in Tables 1 and 2 and in Experimental.     

Ion-containing reverse osmosis membranes obtained by radiation grafting method

Cationic membranes obtained by radiation grafting of acqueous acrylic acid onto low density polyethylene films followed by alkaline treatment to confer ionic character in the graft chains, were tested for reverse osmosis desalination of saline water. Selected physical properties of such membranes were investigated. The grafted membranes prossess good mechanical and electrical properties. Water uptake for the alkali-treated membrane was much higher than that of the alkali-untreated one. The effect of operation time, degree of grafting, applied pressure and feed concentration on the water flux and salt rejection for the grafted membranes was investigated. Such cationic membranes showed good durability, thermal and chemical stability, acceptable water flux and salt rejection which may make them acceptable for practical use in reverse osmosis desalination of sea water.     

Application of complementary mass spectrometric techniques to the identification of ketoprofen phototransformation products

Ketoprofen (KP) is a nonsteroidal anti-inflammatory drug, which during UV irradiation rapidly transforms into benzophenone derivatives. Such transformation products may occur after topical application of KP, which is then exposed to sunlight resulting in a photo-allergic reaction. These reactions are mediated by the benzophenone moiety independently of the amount of allergen. The same reactions will also occur during wastewater or drinking water treatment albeit their effect in the aqueous environment is yet to be ascertained. In addition, only a few such transformation products have been recognised. To enable the detection and structural elucidation of the widest range of KP transformation products, this study applies complementary chromatographic and mass spectrometric techniques including gas chromatography coupled to single quadrupole or ion trap mass spectrometry and liquid chromatography hyphenated with quadrupole-time-of-flight mass spectrometry. Based on structural information gained in tandem and multiple MS experiments, and on highly accurate molecular mass measurements, chemical structures of 22 transformation products are proposed and used to construct an overall breakdown pathway. Among the identified transformation products all but two compounds retained the benzophenone moiety--a result, which raises important issues concerning the possible toxic synergistic effects of KP and its transformation products. These findings trigger further research into water treatment technologies that would limit their entrance into environmental or drinking waters.     

Facile fabrication of a superamphiphobic surface on the copper substrate

A simple solution-immersion technique was developed for the fabrication of a superamphiphobic surface on the copper sheet. Hierarchical structure composed of nanorod arrays and microflowers was formed on the copper surface by an alkali assistant oxidation process; after fluorination, the surface became super-repellent toward water and several organic liquids possessing much lower surface tension than that of water, such as hexadecane. Such superamphiphobicity is attributed to the synergistic effect of their special surface chemicals and microscopic structures, which allows for the formation of a composite interface with all probing liquids tested. We also discuss the effects of surface chemical constituent and geometrical structure on hydrophobicity and oleophobicity; such information allows us to engineer surfaces with specific oleophobic behavior. Additionally, the stability of the composite interface on the created superamphiphobic surface is studied by the compression and immersion test.     

Free radical-scavenging activity of indolic compounds in aqueous and ethanolic media

Indolic compounds are a broad family of substances present in microorganisms, plants and animals. They are mainly related with tryptophan metabolism, and present particularities that depend on their respective chemical structures. The most important members of the family are the plant hormone, indole-3-acetic acid, and the animal hormone, melatonin. An important characteristic of some indolic compounds is that they may be useful as chemical preventive agents against diseases such as cancer, oxidative stress, etc. For this reason, the possible antioxidant activities (free radical-scavenging activity) of several indoles were studied. The2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid /H(2)O(2)/HRP decoloration method was applied to determine both hydrophilic (in buffered media) and lipophilic (in organic media) antioxidant properties of the indolic compounds. Also, a study of the hydrophilic antioxidant activities of indoles at different pH values (between 4.5 and 8.5) was made. Finally, their possible role as diet plant antioxidants is discussed.     

The Formation of Middle-Phase Microemulsions of Polar Oils

Middle-phase microemulsions exhibit the unique properties of an ultra-low interfacial tension and a bicontinuous structure formed from the water and oil components. New developments exploiting these properties are described. In designing such systems, it is important that the spontaneous transition of the oil droplets from Winsor II through Winsor III to the Winsor I state is brought about by diffusion or chemical reaction. The selection of the hydrophobic and lipophilic surfactants is critical when low-energy emulsification systems for highly polar oils are being developed.     

Lipophilic oligonucleotides spontaneously insert into lipid membranes, bind complementary DNA strands, and sequester into lipid-disordered domains

For the development of surface functionalized bilayers, we have synthesized lipophilic oligonucleotides to combine the molecular recognition mechanism of nucleic acids and the self-assembly characteristics of lipids in planar membranes. A lipophilic oligonucleotide consisting of 21 thymidine units and two lipophilic nucleotides with an alpha-tocopherol moiety as a lipophilic anchor was synthesized using solid-phase methods with a phosphoramadite strategy. The interaction of the water soluble lipophilic oligonucleotide with vesicular lipid membranes and its capability to bind complementary DNA strands was studied using complementary methods such as NMR, EPR, DSC, fluorescence spectroscopy, and fluorescence microscopy. This oligonucleotide inserted stably into preformed membranes from the aqueous phase. Thereby, no significant perturbation of the lipid bilayer and its stability was observed. However, the non-lipidated end of the oligonucleotide is exposed to the aqueous environment, is relatively mobile, and is free to interact with complementary DNA strands. Binding of the complementary single-stranded DNA molecules is fast and accomplished by the formation of Watson-Crick base pairs, which was confirmed by 1H NMR chemical shift analysis and fluorescence resonance energy transfer. The molecular structure of the membrane bound DNA double helix is very similar to the free double-stranded DNA. Further, the membrane bound DNA double strands also undergo regular melting. Finally, in raft-like membrane mixtures, the lipophilic oligonucleotide was shown to preferentially sequester into liquid-disordered membrane domains.     

Spontaneous two-dimensional spherical colloidal structures

Two-dimensional spherical crystalline colloidal structures are formed at the interface between water and oil as the result of spontaneous emulsification and colloidal self-assembly. When water droplets are introduced in oil containing a lipophilic surfactant, smaller water droplets of uniform size are spontaneously produced at the spherical interface. Initially of submicrometer size, the small droplets at the interface self-assemble, forming ordered structures, and grow uniformly with time until they reach a size of a few micrometers, maintaining the crystalline structure.     

Synthesis and Evaluation of New Demulsifiers Incorporating Linear Alkyl Benzene Moiety for Treating Water-in-Oil Emulsion

In the present study, five types of water soluble demulsifiers based on linear alkyl benzene were prepared. The chemical structures of the prepared demulsifiers were elucidated using Fourier transform-infrared (FTIR) and ¹H NMR spectra. Different factors affecting demulsification efficiency such as; water content, demulsifier concentration, hydrophilic lipophilic balance (HLB), and ethylene oxide unit were investigated. Also, the rheological properties in relation to demulsification efficiency were studied. The surface and thermodynamic parameters of the prepared demulsifiers were determined at 25°C including, surface tension (γ) and effectiveness, maximum surface excess (Γ_max), and minimum surface area (A_min). From the obtained data, it was found that the demulsification efficiency increases with increasing the water content and concentration of the demulsifiers. Primarily evaluation study of demulsification performance of the new demulsifiers showed that as the ethylene oxide unit in the demulsifiers increase (10–40 ethylene oxide units), the performance of the demulsifiers increasing, however, it decrease in case of demulsifiers with (80 ethylene oxide unit).     

Water at Biological Interfaces - Structural and Functional Aspects

Abstract

The structure of water near interfaces is reviewed in this paper and evidence presented for the existence of notable changes in the properties of such vicinal water. The depth of the changed surface zone is discussed; it appears that this depth may approach a tenth ofa micron. Possible types of vicinal water structures include the high-pressure ice polymorphs and clathrate. cage-like entities. Some examples of thermal anomalies in the properties of vicinal water are reviewed: at least four different thermal anomalies occur between the freezing and boiling point. It is concluded that thex anomalies likely reflect higher order phase transitions in the structured units of the vicinal water. These transitions appear not to be notably affected by the detailed chemical nature of thc solid substrates with which thc ater is in contact. This is referred to as the “paradoxical effect” and is tentatively interpreted in terms of an energy delocalization phenomenon. The vicinal water structures near solid interfaces appear characterized by low energetics and long-range ordering: these vicinal structures may represent the “anti-crystalline” state discussed by Ubbelohde. The importance of such structures in biological systems is examined. Examples are shown of thermal anomalies in the properties of cellular systems. and the role of water in cell physiology is reviewed. including aspects of water/macromolecule interactions, gene action, mechanism of thermal death, and active transport, etc. Non-equilibrium aspects of biological systems are considered briefly in terms of the “dissipative structures” discussed by Glansdorffand Prigogine, and the suggestion is made that the domains of local ordering which may occur as thc result of conditions very far from equilibrium may specifically and uniquely involve the intracellular structurally moditied water.     

Straightforward Oxidation of a Copper Substrate Produces an Underwater Superoleophobic Mesh for Oil/Water Separation

A superhydrophilic and underwater superoleophobic Cu(OH)₂‐covered mesh with micro‐ and nanoscale hierarchical composite structures is successfully fabricated through a one‐step chemical oxidation of a smooth‐copper mesh. Such mesh, without any further modification, can selectively separate water from oil/water mixtures with high separation efficiency, and possess excellent stability even after 60 uses. This method provides a simple, low‐cost, and scalable strategy for the purification of oily wastewater.     

Electrochemistry in bicontinuous microemulsions based on control of dynamic solution structures on electrode surfaces

Bicontinuous microemulsions (BMEs, Winsor III), also called middle-phase microemulsions, are low-viscosity, isotropic, thermodynamically stable, and spontaneously formed mixtures of water, oil, and surfactants. They are unique solution media for electrochemistry. Here, we introduce the recent progress in the electrochemistry of BMEs from their fundamental aspects to their practical applications. Electrochemistry using BMEs has two irreplaceable properties: the coexistence of hydrophilic and lipophilic species with high self-diffusion coefficients; and the dynamic deformation of structures at an oil/water/electrode ternary interface, which is easily changed according to the property of the electrode surface. Electrochemical contact with the micro-saline and oil phases in a BME is alternately or simultaneously achieved by controlling the hydrophilicity and lipophilicity of the electrode surfaces. The selective electrochemical analysis of hydrophilic and lipophilic antioxidants in liquid foods without extraction demonstrated as the use of the unique ternary solution structures of BME on solid surfaces.